A solid polymer type fuel cell generates a power by a chemical reaction between hydrogen in a fuel gas supplied to an anode and oxygen in an oxidizing gas supplied to a cathode. In this electrochemical reaction, water is formed on a cathode side. When the fuel cell is left to stand in the environment at a low temperature of 0° C. or less from the system stop to the next system start, the next system start is not satisfactorily performed or requires much time owing to the influence of the formed water which has frozen in the fuel cell.
Japanese Patent Application Laid-Open No. 2005-251576 discloses a control method for decreasing the water content of the fuel cell at the system stop so as to secure stable start properties even in the environment at the low temperature. In this control method, after the system stop is instructed, an outside air temperature sensor detects an outside air temperature, and the possibility of the freezing within 24 hours is judged based on the outside air temperature. Moreover, when the possibility of the freezing is present, the oxidizing gas is supplied to the fuel cell by an air compressor to discharge the water content from the fuel cell. Such scavenging processing of the fuel cell is performed until an electrolytic film dries up.